Recently, polymer actuators (soft actuators) that can be driven at a low voltage of about several volts and have light weights and excellent flexibility have been developed. The driving systems of actuators are roughly classified into expansion/contraction drive and bending drive. The expansion/contraction drive hardly causes buckling and is suitable for application to pushing movement.
As the expansion/contraction type actuator, an ion conducting actuator using a change in volume of an electrically conductive polymer such as polypyrrole or polyaniline is known. The change in volume of the electrically conductive polymer is based on taking in and out of electrolyte ions (dopant ions) in an electrolytic solution due to an oxidation-reduction reaction.
That is, electrolyte ions in an electrolytic solution are accumulated in an electrically conductive polymer layer or accumulated ions are released to the electrolytic solution, by voltage application. As a result, the electrically conductive polymer layer expands or contracts and thereby functions as an elastic electrode layer.
PTL 1 describes a configuration in which a plurality of expansion/contraction devices having a voltage-applying section is disposed in a cylindrical counter electrode section, and, inside the cylindrical counter electrode section, the space between the inner circumference of the counter electrode section and the outer surfaces of the expansion/contraction devices having the voltage-applying section is filled with an electrolyte.